Cryptology ePrint Archive: Report 2007/069

Abstract: Since the introduction of nominative signature in 1996, there have been only a few schemes proposed and all of them have already been found flawed. In addition, there is no formal security model defined. Even more problematic, there is no convincing application proposed. Due to these problems, the research of nominative signature has almost stalled and it is unknown if a secure nominative signature scheme can be built or there exists an application for it. In this paper, we give positive answers to these problems. First, we illustrate that nominative signature is a better tool for building user certification systems which are originally believed to be best implemented using a universal designated-verifier signature. Second, we propose a formal definition and a rigorous set of adversarial models for nominative signature. Third, we show that Chaum's undeniable signature can be transformed efficiently to a nominative signature and prove its security.